High strength fabrications of aluminum base alloys containing copper



United States Patent This invention relates to aluminum base alloys and more particularly concerns a novel aluminum base alloy having special utilityin the preparation of high strength fabricated articles thereof, and the process for preparing these articles.

Though in general, aluminum base alloys containing copper possess only moderate strength, they are sufficiently strong for certain applications. In other applications requiring higher strength, however, these alloys have heretofore been limited in their utility.

The object of the present invention, therefore, is to provide a novel aluminum base alloy containing copper and capable of being processed to obtain high strength fabrications t-hereof, and the process for preparing these high strength fabrications.

A novel aluminum base alloy containing copper has now been developed in accordance with the invention wherein the strength has been substantially increased by incorporating therein certain other alloying metals, hereinafter referred to as additive metals, in a specific concentration range which is related to the copper content of the alloy, and processing the so -prepared novel alloy under particular conditions to obtain optimum strength.

All percentages referred to throughout this specificati-on are by weight unless otherwise indicated.

In general, this novel aluminum base alloy contains from at least 4 and preferably at least percent of copper to about percent of copper. The particular amount of copper used depends on the amount and kind of additive metal employed such metal being one selected from the group consisting of calcium, chromium, iron, manganese, mischmetal, nickel, and silicon. The amount of additive metal is generally between 0.3 and 10 percent of the alloy. The balance of the alloy is aluminum.

The minimum amount of copper employed in the alloy is as aforesaid dependent upon the amount of the additive metal if any and is determined in accordance with the empirical equation:

Weight percent copper=4.0 +KX where X is the weight percent in the alloy of the selected additive metal and K is a constant whose value depends upon the particular additive metal used and the copper content of the alloy, the values for K being hereinafter tabulated as shown in Table I. Preferably, however, the minimium amount of copper to be employed in the alloy is obtained by modifying the above equation by substituting therein 5 for the 4.

In Table I below, examples of both the oyerable and preferred concentration ranges for each additive metal, and the corresponding K values therefore are set forth. The 2nd and 3rd columns of proportions are for alloys containing 4% of copper and the 4th and 5th columns are for alloys containing 5% of copper.

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TABLE I Operable Preferred Additive Metal Range K. Factor Range K. Factor Caleium 0.4- 2.2 5.0 0. 5-1.25 8.0 Chromium 0.3- 4. 0 0.5 1.0-3.0 1.0 Iron 1 25- 5. 0 2.0 2. 0-4.0 2. 5 Manganese 1. 5- 6. 0 0.5 2. 0-4. 0 0.8 Mischmetal 0.5- 7.3 1. 5 1.0-5.0 2.0 NickeL- 0. 5-10. 0 1. 3 1. 0-6. 0 1. 7 Silicon 1 5-10. 0 0 2.0-5. 0 0

Depending on the effect desired, other alloying elements conventionally employed can be added to the alloy of the present invention without detracting from its excellent strength properties. In carrying out the present invention, the novel aluminum base alloy as specified herein is prepared by using the alloying and melting techniques commonly employed 20 in the aluminum art. Highly desirable properties are obtained by rapidly solidifying the molten alloy as, for example, by jet or disc type atomizing devices either in cool air or in a cool inert atmosphere such as, for example, argon. The molten alloy may also be cast into ordinary ingots. However, the strength values thereby obtained are generally less satisfactory than when thinwalled cold molds are used. When the alloy is prepared by atomizing or pelleting, it is preferred to convert this into massive metal by die expression to obtain maximum properties in fabricated articles, using normal extrusion techniques and equipment. If desired, however, other fabrication methods may be used such as, for example, rolling, forging, or, as above mentioned, casting into thinwalled molds. In the latter method both rapid quenching and fabrication are accomplished in the same operation.

In extruding, the pellets are normally preheated to a temperature within the range of from about 600 F. to about 1000 F., and the extrusion container is at a temperature of from about 500 F. to about 850 F. If desired, the pellets may be precompa cted prior to extruding.

In order to obtain optimum strength, regardless of the method of fabrication employed, the alloys of the present invention must thereafter be solution heat treated, rapidly quenched, and aged. Solution heat treating may be accomplished at a temperature within the range of from about 900 F. to about 1000 F. for a period of about one minute or more, followed by rapid quenching and aging the quenched article at a temperature of from about 300 to about 400 F. for a period of from about 5 hours to about 20 hours. Normally the extrude is solution heat treated at about 950 F. for about 15 minutes, water quenched, then artifically aged at 340 F. for 16 hours. However, different heat treatment combinations can be employed, depending on the alloy system being used and the properties desired, without departing from thescope and substance of the invention. If desired, the extrude may be quenched as it emerges from the die then subsequently aged, rather than solution heat treated, quenched, then aged.

The term fabrication as used herein refers to mechanical working procedures such as extruding, casting, rolling, forging, and spinning.

The following examples serve to further illustrate the present invention.

3 I Example 1 A number of aluminum lbase alloys containing copper were prepared, each containing a predetermined amount of an additive metal listed in Table I above being a member selected from the group consisting of calcium, chromium, iron, manganese, mischmetal,

nickel, and silicon, the minimum percent of copper being within the range of from about 4.0 to about l within the herein specified ranges, and in a proportion 1 ;253:3 and determmed In accordance Wlth'the relative to that of copper in accordance with the above q I equation. Each alloy was either cast into ingots (I) 3 Wt. percent copper=4+KX inches in diameter or atomized into pellets (P) having a Size suchthat about 85% of the pellets passed through where X is the concentration of the selected add1- a No. 20 sieve and was retained on a No. 200 sieve tlvelnetel and the correspondmg K Value for each (US. Standard sieve, fine), while" the remainder passed addltwe Is as follows:

.through the No. 200 sieve. Calcium 5 Both the ingots and pellets of the above prepared Chromium 5 alloy compositions were extruded by first preheating to Iron 2 about 800 F. then placing the material in the con- M.mganese 5 tainer of a ram extruder, the container being about the Mischmetal 1. 5 same temperature as the pellets, and extruding at a Nickel 13, rate of about 5 feet per minute into strip having a Silicon 0 rectangular cross section 0.2 inch by 1.0 inch. The I resulting strips were then solution heat treated at 950 (2) solidifying the so-prepared aluminum base alloy F. for one hour, quenched, then aged for 16 hours molten droplets; at 340 F. (3) and fabricating said alloy into a useful shape by For comparison both ingots and pellets of the same rolling or forging, thereby providing a high strength aluminum base alloy but without any additive metals, 5 aluminum base alloy article. were extruded under the same conditions as above, in- 2. The process of claim 1 and including the steps of eluding heat treatment and aging. subsequently solution heat treating, rapidly quenching,

Standard test bars of all the alloys prepared as above' and aging the fabricated article. were made, and tested at room temperature, including 3. The process of claim 2 wherein, the solution heat the blank or controls aforementioned for comparison, treating is carried out at a temperature within the range inorder to record percent elongation (percent E) (using of from about 900 F. to about 1000 F. tor a periodof a 2 inch gauge length), tensile strength (TS), and tensile time of at least about 1 minute, and rapidly quenching yield strength (TYS) (at 0.2% ofiset). Representative the extrude, followed by aging at a temperature within results of these tests are presented in Table H which the range of from about 300 F. to about 400 F. for follows: a period of time of from about 5 to about 20 hours.

' TABLE II 1,000 p.s.i.

Example Percent Percent Form Percent E Cu Additive .TYS TS (Blank) 5.0 2.0 Ca I 15 13 30 (1 12.0 1.0 Ca I 10 43 02 12.0 1.0 Ca P 0 51 70 5.0 2.0 Cr I 11 27 30 8.0 2.0 Cr. I s 52 8.0 2.0 Cr P 7 72 7.5 2.0Fe I 15 20 42 9.5 2.0 Fe.-- I 10 38 55 10.0 2.0 Fe.-- I s 51 70 4.5 3.0 Mn- P 9 2s 53. 7.0 3.0Mn I 10 40 55 8.0 3.0Mn P 0 54 74 5.0 5.0MM I 17 12 34 10.0 3.0MM I 12 39 00 5.0 3.0 Ni I 20 11 33 10.0 3.0 Ni I 10 39 50 15.0 3.0Ni P 5 52 70 5.5 5.0 si P 10' 50 59 1 P.s.i. =pounds per square inch of cross section.

It is understood that the copper content in some 4. The process of claim 1 wherein, the weight concenexamples given above may represent an excess of copper tration of the selected additive metal in the aluminum with an additive metal over the minimum amount as base alloy of step 1) is from about 0.4. to about 2.2 required in accordance with. the above equation. percent for calcium, from about 0.3 to about 4.0 percent The figures of the blanks in Table II illustrate the 60 for chromium, from about 1.25 to about 5.0 percent for lower strength resulting because of msuflicient copper iron, from about 1.5 to about 6.0 percent for manganese, 111 tha f y- In contrast alloys the lflventloll as from about 0.5 to about 7.3 percent for misohmetal, from Show P E 1 to 12 lnfllll'slve have 111811 Strength about 0.5 to about 10.0 percent for nickel, and from due to the addition of certain metals when suflicient about 5 to about 101) for Silicon c/opper isthprzesenti1 as protgided for under tlfie pglesegl 5. A process for preparing high strength aluminum en a percen or more or Pre era y base alloy pellet extrusions which comprises: cent or more, but less than 15% of copper. 1 d

I claim: provi ing in EItOIIllZC or pelleted form an alumi- 1' A process for preparing high strength aluminum num base alloy consisting essentially of from about base alloy articles which comprises. 4.0 to about 15 percent copper, from about 0.3 to

(1) preparing an aluminum base alloy in molten drop- 10 Rel-Cent an "i f metal; the balance let form consisting essentially of from about 4.0 to bemg alummum, sald metal bemg f member about 15 weight percent copper, fr about 3 selected from the group consisting of calcium, chroto about 10.0 weight percent of an additive metal, mium, iron, manganese, mischmetal, nickel, and Silithe balance being aluminum, said additive metal Con, t minimum Percent PP- being Within the range from about 4.0 to about 15.0 percent and determined in accordance with the equation:

Wt. percent copper=4+KX where X is the concentration of the selected additive metal and K for each of said additives is as follows:

Calcium 5.0 Chromium 0.5 Iron 2.0 Manganese 0.5 Mischmetal 1.5 Nickel 1.3 Silicon (2) extruding the atomized or pelleted aluminum base alloy thereby to produce a high strength aluminum extrusion.

6. The process of claim 5 wherein, the extrusion temperature is from about 600 F. to about 1000 F.

7. The process of claim 5 and including the steps of subsequently solution heat treating, rapidly quenching, and aging the extrusion product.

8. The process of claim 7 wherein the solution heat treating is carried out at a temperature within the range from about 900 F. to about 1000 F. for a period of time of at least about 1 minute, and the extrude quenched,

6 followed by aging at a temperature within the range from about 300 F. to about 400 F. for a period of time of from about 5 to about 20 hours.

9. The process of claim 6 and including the steps of quenching the extrude, and subsequently aging the soquenched extrude.

References Cited by the Examiner OTHER REFERENCES Alcoa Structural Handbook, 1958, page 34.

DAVID L. RECK, Primary Examiner.

H. F. SAITO, Assistant Examiner. 

1. A PROCESS FOR PREPARING HIGH STRENGTH ALUMINUM BASE ALLOY ARTICLES WHICH COMPRISES: (1) PREPARING AN ALUMINUM BASE ALLOY IN MOLTEN DROPLET FORM CONSISTING ESSENTIALLY OF FROM ABOUT 4.0 TO ABOUT 15.0 WEIGHT PERCENT COPPER, FROM ABOUT 0.3 TO ABOUT 10.0 WEIGHT PERCENT OF AN ADDITIVE METAL, THE BALANCE BEING ALUMINUM, SAID ADDITIVE METAL, BEING A MEMBER SELECTED FROM THE GROUP CONSISTING OF CALCIUM, CHROMIUM, IRON, MANGANESE, MISCHMETAL, NICKEL, AND SILICON, THE MINIMUM PERCENT OF COPPER BEING WITHIN THE RANGE OF FROM ABOUT 4.0 TO ABOUT 15.0 PERCENT AND DETERMINED IN ACCORDANCE WITH THE EQUATION: 